Pb-acid storage batteries, among others, generate gases within the innards of the battery during the normal cycling thereof. These gases are vented to the atmosphere via venting systems designed to permit gas passage while trapping electrolyte. Such systems include provisions for draining any trapped electrolyte back into the battery cells from whence it came.
Battery venting systems geneerally take two forms, i.e. vertical or horizontal depending on the orientation of the chamber in which the electrolyte is trapped. In this regard, both systems typically include a chamber, of one sort or another, located between a cell vent/drainage aperture and a gas exhaust port leading to the atmosphere. The chamber traps electrolyte emanating from the cell vent and prevents it from traversing to the exhaust port and escaping the battery. Electrolyte collected in the trapping chamber drains back into the cell usually through the same aperture used to vent the cell.
Discrete vent plugs found on many batteries exemplify vertical vent systems. The plugs typically include a deep, cylindrical chamber which fits tightly into the filler well of the battery. The floor of the chamber slopes toward an aperture through which the gases vent upwardly and the electrolyte drains back into the cell. The top of the chamber has an exhaust port for discharging the gas to the atmosphere. The chamber may also contain a variety of internal baffles to prevent electrolyte from reaching the exhaust port. Separation of the electrolyte from the gas occurs primarily by gravity as the gases rise through the cylindrical chamber and the heavier electrolyte falls to the chamber floor.
Horizontal vent systems, on the other hand, are most frequently formed integrally with the battery cover and usually pass the gases through an elongated chamber extending horizontally across the top of the battery before discharging it to the atmosphere at a location laterally remote from the cell vent/drainage aperture. Frequently such designs employ a single exhaust port serving several trapping chambers. Such horizontal systems may include a shallow vertical cylindrical portion depending from the cover as part of its electrolyte trapping chamber. one illustration of such a system is found in the "Freedom Battery" manufactured and sold by the assignee of the present invention.
The venting systems such as described above, frequently utilize very small (i.e., typically Ca. 1 mm-3 mm) venting/drainage apertures in the trapping chamber floor to minimize entry of splashing electrolyte into the trapping chambers while permitting the gases to pass. None-the-less, the trapping chambers are commonly invaded by electrolyte entering up through the venting/drainage aperture as a result of excessive overcharging, sloshing, splashing etc. (i.e., due to mishandling, vibration, tilting, or the like). While these small apertures permit gas passage and reduce electrolyte passage they are not conducive to optimum drain back of electrolyte into the battery cells. In this regard, the surface tension between the electrolyte and the rim of the drainage aperture (i.e., capillary effect) tends to hold the electrolyte in the aperture--much like a liquid plug--until such time as an overpowering head of electrolyte accumulates on the floor of the chamber above. While accumulation of electrolyte in the trapping chambers of any venting system is undesirable it is a particularly acute problem in horizontal systems. In this regard, accumulated electrolyte in horizontal chamber systems can more readily traverse the trapping chamber and reach the exhaust port than in vertical chamber systems.
It is the principal object of the present invention to improve electrolyte drainage from the electrolyte trapping chambers of battery gas venting systems. It is a further object of the present invention to concurrently better protect the trapping chambers from electrolyte invasion from the battery innards due to sloshing, splashing or the like. These and other objects and advantages of the present invention will become more readily apparent from the description thereof which follow.